Heavy duty, off-the-road vehicles utilize crawler tracks to provide better mobility on uneven ground and for improved traction. In the usual arrangement, the tracks comprise a plurality of links formed together in an endless chain-type fashion with pads formed on the links for engagement with the ground. The multiple pads along the lower run of the endless track in engagement with the ground at any one time provide exceptional traction, while the upper run serves to recirculate the track. Driven sprockets engage the inner surfaces of the links to drive the track along an endless path and thereby provide movement to the vehicle.
While crawler tracks are quite useful when the vehicle is moving about the job site in a traveling mode, they are not well-suited for use in over-the-road or highway travel. Consequently, the vehicle is normally transported on a tractor trailer from one site to the next. In many cases, over-the-road transport requires removing the entire assembly supporting and driving the crawler tracks from the vehicle to comply with governmental regulations on maximum vehicle width (and possibly placing them on a different tractor trailer altogether to comply with maximum weight restrictions). Since this operation is costly, a significant sought after advantage is of course the ability to complete it in a very short time such that the construction company can make the most efficient use of their capital equipment. In the past, this and other quick assembly type of features have been a particular focus for design of many types of vehicles, including not only light-to-medium duty cranes, but also heavy duty crawler cranes.
The present applicant has previously proposed a system allowing for the easy and efficient, yet secure attachment of crawler track assemblies to heavy-duty crawler cranes using a “hook and pin” type arrangement. In one version of this arrangement, a hook is provided on a first structure projecting from the crawler track assembly for engaging a transverse pin supported by a corresponding structure on the crane. The engagement between the hook and pin helps to ensure that proper alignment is achieved between a matching pair of apertures formed in the corresponding structures. A connector is then positioned in the aligned apertures to establish the connection between the crawler track assembly and the crane.
While this system has enjoyed considerable success from a commercial standpoint, one factor remains a particular hindrance. Specifically, in the past, there has typically been only a single mounting position available for the crawler track assemblies on such cranes. Hence, use of the crane at locations where space is limited, such as between buildings in an urban environment, has been a problem. Even in cases where space is not a concern, having the crawler tracks always mounted in a fixed position close to the vehicle is deleterious, since this reduces the moment arm and limits the loading capabilities. A comparable connection system with similar limitations in disclosed in U.S. Pat. No. 5,823,279 to Petzold, the disclosure of which is incorporated herein by reference.
In recent years there has been some development in making crawler tracks or like structures laterally adjustable. An early example is found in Caterpillar's U.S. Pat. No. 3,998,286 to Ponikelsky et al., which discloses an excavator with a pair of laterally extendable crawler track assemblies. While this arrangement allows for moving the crawler track assemblies between extended and retracted mounting positions and helps to ensure that proper alignment is achieved in both positions, it has several shortcomings. First of all, the upstanding pins serving as connectors are provided on the crawler tracks and are received in corresponding narrow-width slots in the carbody of the excavator. Consequently, in the case where the crawler track assemblies are removed, such as for over-the-road travel, reattachment requires positioning the crawler tracks in a very precise alignment relative to one another and then lowering the entire upper works of the excavator into place such that the pins are received directly in the narrow slots. Moreover, in view of the specific types of structures required and their special arrangement, it is observed that it is not easily retrofitted onto existing excavators or cranes, as a significant overhaul would be required. An earlier, similar proposal is found in Caterpillar's U.S. Pat. No. 3,899,038 to Griffith et al.
A second, more recent example is found in U.S. Pat. No. 4,341,276 to Furichi, which provides a system in which crawler tracks can be mounted in one position or another on a light-duty excavator. While this system seemingly solves the major problem with the approach disclosed in the '286 patent, there is need for improvement in the area of aligning the apertures for receiving the connectors, such as pins, in both the extended and retracted positions. Like the arrangement shown in the '286 patent, this connection system is also not readily adaptable for retrofitting onto existing vehicles without extensive drilling, welding, or other metalworking. A similar, but much earlier arrangement that generally suffers from the same shortcomings is found in U.S. Pat. No. 1,705,578 to Lichtenberg.
Accordingly, a need is identified for an improved manner of connecting one or more removable ground-engaging motive devices, such as crawler track assemblies or like wheeled structures, to a vehicle, such as a crane, excavator, or like lifting or moving device, so that a lateral position adjustment can be easily and efficiently made. Specifically, the arrangement provided would allow for the easy and efficient mounting of the motive device in at least two positions: one close to the body of the vehicle and one farther away from the body of the vehicle. In the case where the vehicle is a crane, the closer or retracted mounting position would allow for the use at locations where space is limited, while the second, extended position would improve the loading capabilities of the boom (especially when in traveling mode). The mounting arrangement would also be easy and inexpensive employed on certain existing vehicles having the hook and pin type of connection system without the need for extensive retrofitting. Overall, the systems and methods would result in a substantial improvement over the above-referenced proposals made by others.